These papers provide the first human data to support a scientific hypothesis suggested at the 7th International Cord Blood Society Congress in 2004. Researchers were already using bone marrow derived MSC’s to enhance HSC transplantation and therefore postulated that umbilical cord tissue MSC’s may be able to support haematopoiesis and enhance engraftment of the cord blood unit and several animal studies have supported this hypothesis.¹˒ ²˒³

These two Chinese studies used culture expanded MSC’s (perhaps native MSC’s may be more potent than culture expanded cells). They compared patients who were co-transplanted with UC-MSC and CB-HSC to patients transplanted with CB-HSC alone.They showed that co-transplanted patients had significantly faster immune recovery and engraftment time (similar to that of a bone marrow transplant). This is a significant finding as cord blood transplants often take approximately 10 days longer to engraft than bone marrow stem cell transplants.⁴˒⁵

According to our present understanding bone marrow contains MSC’s, osteoblasts and other stromal cells (including sinusoidal and endothelial cells) that are responsible for supporting haematopoiesis and cord tissue contains similar cells. MSC’s have been shown to support in vivo haematopoiesis as well as displaying potent immune-suppressive effects.⁶

The mechanisms underlying their immunomodulatory action have not been fully elucidated but complex interactions with several immune cells such as natural killer cells, monocytes, dendritic cells and regulatory T cells are postulated. The four properties of MSc’s that are currently considered most important to their clinical uses are⁷:

1. Their ability to migrate to sites of inflammation following intravenous infusion

MSC’s appear to be safe and well tolerated in cell therapy and are currently being investigated to treat patients with steroid-resistant Graft vs Host Disease (GVHD). Bone marrow MSC’s have been shown to be immune-suppressive but require invasive procedures to harvest them. Umbilical Cord MSC’s are harvested more easily and in one study showed superior proliferative potential and more suppressive effects than compared to bone marrow MSC.⁸

Hopefully these studies will pave the way for more extensive clinical trials using the combination of UC-MSC and CB-HSC in improving the outcomes of cord blood transplants.